1. Field of the Invention
The field of the invention is that of input keyboards.
2. Description of the Prior Art
Many electronic devices include a microprocessor connected to a keyboard with input keys enabling their users to send them instructions or commands. For example, certain keys may be dedicated to entering a letter of an alphabet and/or a digit and/or a punctuation mark, while other keys may be dedicated to movement in selected directions (and are then referred to as “navigation” keys).
In the present context, the expression “electronic device” means any device equipped with a man/machine interface for input of information or commands, for example a fixed or portable computer (where applicable of the onboard type), a fixed or mobile telephone, a personal digital assistant (PDA), a guidance or navigation device, or a video games console.
For the microprocessor to be able to determine (or recognize) an input key that has just been actuated, it has a certain number of connecting pins to which are connected, for example via a bus, connecting terminals that are themselves connected to conductive lines connected to the various keys.
Because the microprocessor has a limited number of connecting pins, there has previously been proposed a keyboard using a “grid” connection architecture. To be more precise, this type of keyboard comprises: i) primary and secondary conductive lines connected to respective primary and secondary connecting areas and to a connecting terminal intended to be connected to a device microprocessor, and ii) input keys each of which can establish, when operated, contact between one of the primary areas of one of the primary lines and one of the secondary areas of one of the secondary lines so as to place these primary and secondary lines in a “high” logic state (for example a logic state equal to 1). If the microprocessor detects high states on two of its connecting pins, it merely has to access a table establishing a correspondence between key identifiers, primary line identifiers and secondary line identifiers to determine the identifier of the operated key that caused the connecting terminals connected to the two connecting pins to be placed in the high state.
For example, the microprocessor detects a short circuit between a secondary line (for example a secondary line serving as an input line) and a primary line (for example a primary line serving as an output line) brought about by establishing contact between a primary area of that primary line and a secondary area of that secondary line by means of a key. Other types of detection may be envisaged, of course, provided that they are based on the absence or the presence of an analog “signal” (for example an electrical potential) or a digital “signal”.
Thanks to the grid (or matrix) architecture described above, the maximum number K of keys that can be managed by a microprocessor with P connecting pins is equal to the product of the number N of primary connecting lines by the number M of secondary connecting lines (K=N×M), with the constraint that P=N+M. For example, a microprocessor with P=10 connecting pins can manage at most K=25 keys (when N=M=5).
The number of input keys of the keyboard of certain devices cannot be increased because the number of connecting pins of their microprocessor cannot be increased, so that adding functions or commands necessitates configuring the microprocessor so that it can associate each function or command that is added with operation of at least two keys, for example.
For example, if the keyboard includes four navigation keys associated with four “main” directions of movement (north, south, east and west) and there is a requirement to define “intermediate” directions of movement (north-east, north-west, south-east and south-west), the microprocessor must be configured so that it associates each intermediate direction with the successive operation of the two navigation keys that are associated with the combination of main directions that define it. For example, if the device has a navigation function coupled to a joystick and the user orients his joystick in the north-east direction, the joystick must operate the underlying north and east keys within a predefined time period for the microprocessor to interpret this as a double keystroke and to understand that it is the north-east direction that is being requested.
The direction in which the joystick is pointed does not always correspond to the theoretical direction in which said joystick is able to press on the two keys concerned within the time period allowed. Consequently, if the joystick presses on only one of the two keys, the microprocessor understands that the direction requested is that which corresponds to the activated key, which is an error.
Furthermore, this two-fold operation may prove to be incompatible with certain uses requiring fast input of commands, as in certain video games, for example.
The invention therefore proposes to improve on the above situation.